1. I undertand (I guess) Zoho Creator's current inability to serve up subform data (child records data) to small device users where an image field exists in child subform.  
2. Frankly I don't like dealing with subforms anyway, which is why all subforms are disabled and hidden on main form add/edit load and I never add/edit child records via subforms from the main form.

Question:  Why, if a subform [containing image field] is hidden and/or disabled on form load, can the user still not access the the main form from Android or iOS?

To my way of thinking, this makes Zoho useless.  What data set today is not going to have an image field?  But furthermore, if the subform is hidden and disabled, why does Zoho Creator care?  At the very least it should notify the user of the shortcoming, and open the parent form anyway, not giving access to the "offending" child form.

Furthermore, I have learned that if the subforms are later removed from the parent form, and the link is "broken", future pivot reports and other reports that depend on the relationship existing in a certain way, will no longer work properly.  After deleting subform elements, you can still effectively add child records, and most functionality will work as expected, but not all.

So it seems removing the subform [link] is not a viable work-around option, either, especially if you plan on implementing pivot reports and calling in data from related forms.  Learned this the hard way.